Power Saving Glaucoma Drainage Device

ABSTRACT

A glaucoma drainage device has an active valve configured to be located between an anterior chamber of an eye and a drainage location, a power source coupled to the active valve, and a controller coupled to the power source. A first pressure sensor is located in fluid communication with the anterior chamber, a second pressure sensor is located in the drainage location, and a third pressure sensor located remotely from the first and second pressure sensors. The controller reads the first, second, and third pressure sensors once during a period of time and adjusts the active valve to control intraocular pressure.

This application is a continuation-in-part of U.S. application Ser. No.12/685,772 filed Jan. 12, 2010, which is a continuation-in-part of U.S.application Ser. No. 12/609,043 filed Oct. 30, 2009, which is acontinuation-in-part of U.S. application Ser. No. 12/563,244 filed Sep.21, 2009.

BACKGROUND OF THE INVENTION

The present invention relates to a glaucoma drainage device that isoperated so as to conserve power.

Glaucoma, a group of eye diseases affecting the retina and optic nerve,is one of the leading causes of blindness worldwide. Glaucoma resultswhen the intraocular pressure (IOP) increases to pressures above normalfor prolonged periods of time. IOP can increase due to an imbalance ofthe production of aqueous humor and the drainage of the aqueous humor.Left untreated, an elevated IOP causes irreversible damage the opticnerve and retinal fibers resulting in a progressive, permanent loss ofvision.

The eye's ciliary body epithelium constantly produces aqueous humor, theclear fluid that fills the anterior chamber of the eye (the spacebetween the cornea and iris). The aqueous humor flows out of theanterior chamber through the uveoscleral pathways, a complex drainagesystem. The delicate balance between the production and drainage ofaqueous humor determines the eye's IOP.

Open angle (also called chronic open angle or primary open angle) is themost common type of glaucoma. With this type, even though the anteriorstructures of the eye appear normal, aqueous fluid builds within theanterior chamber, causing the IOP to become elevated. Left untreated,this may result in permanent damage of the optic nerve and retina. Eyedrops are generally prescribed to lower the eye pressure. In some cases,surgery is performed if the IOP cannot be adequately controlled withmedical therapy.

Only about 10% of the population suffers from acute angle closureglaucoma. Acute angle closure occurs because of an abnormality of thestructures in the front of the eye. In most of these cases, the spacebetween the iris and cornea is more narrow than normal, leaving asmaller channel for the aqueous to pass through. If the flow of aqueousbecomes completely blocked, the IOP rises sharply, causing a suddenangle closure attack.

Secondary glaucoma occurs as a result of another disease or problemwithin the eye such as: inflammation, trauma, previous surgery,diabetes, tumor, and certain medications. For this type, both theglaucoma and the underlying problem must be treated.

FIG. 1 is a diagram of the front portion of an eye that helps to explainthe processes of glaucoma. In FIG. 1, representations of the lens 110,cornea 120, iris 130, ciliary bodies 140, trabecular meshwork 150, andSchlemm's canal 160 are pictured. Anatomically, the anterior chamber ofthe eye includes the structures that cause glaucoma. Aqueous fluid isproduced by the ciliary bodies 140 that lie beneath the iris 130 andadjacent to the lens 110 in the anterior chamber. This aqueous humorwashes over the lens 110 and iris 130 and flows to the drainage systemlocated in the angle of the anterior chamber. The angle of the anteriorchamber, which extends circumferentially around the eye, containsstructures that allow the aqueous humor to drain. The first structure,and the one most commonly implicated in glaucoma, is the trabecularmeshwork 150. The trabecular meshwork 150 extends circumferentiallyaround the anterior chamber in the angle. The trabecular meshwork 150seems to act as a filter, limiting the outflow of aqueous humor andproviding a back pressure producing the IOP. Schlemm's canal 160 islocated beyond the trabecular meshwork 150. Schlemm's canal 160 hascollector channels that allow aqueous humor to flow out of the anteriorchamber. The two arrows in the anterior chamber of FIG. 1 show the flowof aqueous humor from the ciliary bodies 140, over the lens 110, overthe iris 130, through the trabecular meshwork 150, and into Schlemm'scanal 160 and its collector channels.

In glaucoma patients, IOP can vary widely during a 24 hour period.Generally, IOP is highest in the early morning hours before medicationis administered upon waking. Higher pressures damage the optic nerve andcan lead to blindness. Accordingly, it would be desirable to have anactive glaucoma drainage device that controls IOP.

SUMMARY OF THE INVENTION

In one embodiment consistent with the principles of the presentinvention, the present invention is a glaucoma drainage devicecomprising: an active valve configured to be located between an anteriorchamber of an eye and a drainage location; a power source coupled to theactive valve; and a controller coupled to the power source; wherein thecontroller directs power from the power source to the active valve basedon a pressure.

In another embodiment consistent with the principles of the presentinvention, the present invention is an intraocular pressure sensorsystem comprising: a first pressure sensor located in fluidcommunication with an anterior chamber of an eye; a remote pressuresensor located remotely from the first pressure sensor such that theremote pressure sensor measures or approximates atmospheric pressure; acontroller configured to read the first and second pressure sensors; anda power source coupled to the controller; wherein a difference betweenreadings from the first pressure sensor and the remote pressure sensorapproximates intraocular pressure; and further wherein the controllerreads the first pressure sensor and the second pressure sensor onceduring a time period.

In another embodiment consistent with the principles of the presentinvention, the present invention is an intraocular pressure sensorsystem comprising: a first pressure sensor located in fluidcommunication with an anterior chamber of an eye; a second pressuresensor located in a drainage location; a controller configured to readthe first and second pressure sensors; and a power source coupled to thecontroller; wherein a difference between readings from the firstpressure sensor and the second pressure sensor approximates a pressuredifferential between the anterior chamber and the drainage location; andfurther wherein the controller reads the first pressure sensor and thesecond pressure sensor once during a time period.

In another embodiment consistent with the principles of the presentinvention, the present invention is an intraocular pressure sensorsystem comprising: a first pressure sensor located in a drainagelocation; a remote pressure sensor located remotely from the firstpressure sensor such that the remote pressure sensor measures orapproximates atmospheric pressure; a controller configured to read thefirst and second pressure sensors; and a power source coupled to thecontroller; wherein a difference between readings from the firstpressure sensor and the remote pressure sensor approximates pressure inthe drainage location; and further wherein the controller reads thefirst pressure sensor and the second pressure sensor once during a timeperiod.

In another embodiment consistent with the principles of the presentinvention, the present invention is a glaucoma drainage devicecomprising: an active valve configured to be located between an anteriorchamber of an eye and a drainage location; a power source coupled to theactive valve; a controller coupled to the power source; a first pressuresensor located in fluid communication with the anterior chamber; asecond pressure sensor located in the drainage location; and a thirdpressure sensor located remotely from the first and second pressuresensors; wherein the controller reads the first, second, and thirdpressure sensors once during a period of time.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are intended to provide further explanation of the invention asclaimed. The following description, as well as the practice of theinvention, set forth and suggest additional advantages and purposes ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a diagram of the front portion of an eye.

FIG. 2 is a block diagram of an IOP measuring system according to theprinciples of the present invention.

FIG. 3 is a diagram of an IOP sensor according to the principles of thepresent invention.

FIG. 4 is a diagram of one possible application of the IOP sensor of thepresent invention.

FIG. 5 is an end cap implementation of an IOP sensor consistent with theprinciples of the present invention.

FIGS. 6A and 6B are perspective views of an end cap implementation of anIOP sensor consistent with the principles of the present invention.

FIGS. 7A and 7B are perspective views of a lumen clearing valveaccording to the principles of the present invention.

FIG. 8 is a perspective view of a lumen clearing valve with a fiberclearing member according to the principles of the present invention.

FIG. 9 is a perspective view of a lumen clearing valve with an aqueousdispersion member to clear fibrosis according to the principles of thepresent invention.

FIG. 10 is a perspective view of a lumen clearing valve with hybridexternal member according to the principles of the present invention.

FIGS. 11A and 11B depict an end cap implementation of the valve andpressure sensor system according to the principles of the presentinvention that includes both single and dual lumen versions.

FIGS. 12A and 12B are cross section views of dual tubing that can beused with the system of the present invention.

FIG. 13 is a perspective view of a two lumen valve and pressure sensorsystem according to the principles of the present invention.

FIG. 14 is a perspective view of power generator according to theprinciples of the present invention.

FIG. 15 is an end view of a rotor located in a tube according to theprinciples of the present invention.

FIG. 16 is a diagram of one possible location of a power generator in aglaucoma drainage system according to the principles of the presentinvention.

FIG. 17 is a diagram of another possible location of a power generatorin a glaucoma drainage system according to the principles of the presentinvention.

FIG. 18 is a flow chart of one method of operating the glaucoma drainagedevice of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is now made in detail to the exemplary embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are usedthroughout the drawings to refer to the same or like parts.

FIG. 2 is a block diagram of an IOP measuring system 200 according tothe principles of the present invention. In FIG. 2, the IOP measuringsystem includes power source 205, IOP sensor 210 (which can include P1,P2, and/or P3), processor 215, memory 220, data transmission module 225,and optional speaker 230.

Power source 205 is typically a rechargeable battery, such as a lithiumion or lithium polymer battery, although other types of batteries may beemployed. In addition, any other type of power cell is appropriate forpower source 205. Power source 205 provides power to the system 200, andmore particularly to processor 215. Power source can be recharged via anRFID link or other type of magnetic coupling.

In another embodiment of the present invention, power source 205 is acapacitor that stores charge generated by generator 1410 as explainedbelow. Other types of charge storing or energy storing devices may alsobe employed to implement power source 205. As more fully explainedbelow, generator 1410 is coupled to power source 205.

Processor 215 is typically an integrated circuit with power, input, andoutput pins capable of performing logic functions. In variousembodiments, processor 215 is a targeted device controller. In such acase, processor 215 performs specific control functions targeted to aspecific device or component, such as a data transmission module 225,speaker 230, power source 205, or memory 220. In other embodiments,processor 215 is a microprocessor. In such a case, processor 215 isprogrammable so that it can function to control more than one componentof the device. In other cases, processor 215 is not a programmablemicroprocessor, but instead is a special purpose controller configuredto control different components that perform different functions.

Memory 220 is typically a semiconductor memory such as NAND flashmemory. As the size of semiconductor memory is very small, and thememory needs of the system 200 are small, memory 220 occupies a verysmall footprint of system 200. Memory 220 interfaces with processor 215.As such, processor 215 can write to and read from memory 220. Forexample, processor 215 can be configured to read data from the IOPsensor 210 and write that data to memory 220. In this manner, a seriesof IOP readings can be stored in memory 220. Processor 215 is alsocapable of performing other basic memory functions, such as erasing oroverwriting memory 220, detecting when memory 220 is full, and othercommon functions associated with managing semiconductor memory.

Data transmission module 225 may employ any of a number of differenttypes of data transmission. For example, data transmission module 225may be active device such as a radio. Data transmission module 225 mayalso be a passive device such as the antenna on an RFID tag. In thiscase, an RFID tag includes memory 220 and data transmission module 225in the form of an antenna. An RFID reader can then be placed near thesystem 200 to write data to or read data from memory 220. Since theamount of data typically stored in memory 220 is likely to be small(consisting of IOP readings over a period of time), the speed with whichdata is transferred is not crucial. Other types of data that can bestored in memory 220 and transmitted by data transmission module 225include, but are not limited to, power source data (e.g. low battery,battery defect), speaker data (warning tones, voices), IOP sensor data(IOP readings, problem conditions), and the like.

Optional speaker 230 provides a warning tone or voice to the patientwhen a dangerous condition exists. For example, if IOP is at a levelthat is likely to lead to damage or presents a risk to the patient,speaker 230 may sound a warning tone to alert the patient to seekmedical attention or to administer eye drops. Processor 215 reads IOPmeasurements from IOP sensor 210. If processor 215 reads one or a seriesof IOP measurements that are above a threshold, then processor 215 canoperate speaker 230 to sound a warning. The threshold can be set andstored in memory 220. In this manner, an IOP threshold can be set by adoctor, and when exceeded, a warning can be sounded.

Alternatively, data transmission module may be activated to communicatean elevated IOP condition to a secondary device such as a PDA, cellphone, computer, wrist watch, custom device exclusively for thispurpose, remote accessible data storage site (e.g. an internet server,email server, text message server), or other electronic device. In oneembodiment, a personal electronic device uploads the data to the remoteaccessible data storage site (e.g. an internet server, email server,text message server). Information may be uploaded to a remote accessibledata storage site so that it can be viewed in real time, for example, bymedical personnel. In this case, the secondary device may contain thespeaker 230. For example, in a hospital setting, after a patient hasundergone glaucoma surgery and had system 200 implanted, a secondarydevice may be located next to the patient's hospital bed. Since IOPfluctuations are common after glaucoma surgery (both on the high sideand on the low side which is also a dangerous condition), processor 215can read IOP measurements made by an implanted IOP sensor 210. Ifprocessor 215 reads an unsafe IOP condition, data transmission module225 can alert the patient and medical staff via speaker 230 or bytransmitting the unsafe readings to a secondary device.

Such a system is also suitable for use outside a hospital setting. Forexample, if an unsafe IOP condition exists, processor 215 can operatespeaker 230 to sound an audible warning. The patient is then alerted andcan seek medical attention. The warning can be turned off by a medicalprofessional in a number of ways. For example, when data transmissionmodule 225 is an RFID tag, an RFID link can be established between anexternal device and system 200. This external device can communicatewith system 200 to turn off the speaker 230. Alternatively, an opticalsignal may be read by system 200. In this case, data transmission module225 has an optical receptor that can receive a series of light pulsesthat represent a command—such as a command to turn off speaker 230.

FIG. 3 is a diagram of an IOP sensor according to the principles of thepresent invention. In FIG. 3, the IOP sensor consists of three pressuresensors, P1, P2, and P3, a drainage tube 430, valve 420, and divider350. Pressure sensor P1 is located in or is in fluidic communicationwith the anterior chamber 340, pressure sensor P2 is located at adrainage site in the subconjunctival space, and pressure sensor P3 islocated remotely from P1 and P2. Pressure sensor P1 can also be locatedin a lumen or tube that is in fluid communication with the anteriorchamber. As such, pressure sensor P1 measures a pressure in the anteriorchamber, pressure sensor P2 measures a pressure at a drainage site, andpressure sensor P3 generally measures or corresponds to atmosphericpressure.

In FIG. 3, tube 430 drains aqueous from the anterior chamber 340 of theeye. A valve 420 controls the flow of aqueous through the tube 430.Pressure sensor P1 measures the pressure in the tube 430 upstream fromthe valve 420 and downstream from the anterior chamber 340. In thismanner, pressure sensor P1 measures the pressure in the anterior chamber340. The expected measurement discrepancy between the true anteriorchamber pressure and that measured by P1 when located in a tubedownstream of the anterior chamber (even when located between the scleraand the conjunctiva) is very minimal. For example, Poiseuille's law forpipe flow predicts a pressure drop of 0.01 mmHg across a 5-millimeterlong tube with a 0.300 millimeter inner diameter for a flow rate of 3microliters per minute of water.

A divider 350 separates pressure sensor P2 from pressure sensor P3.Pressure sensor P2 is located at a drainage site (e.g. 410 in FIG. 4).As such, pressure sensor P2 is located in a pocket that generallycontains aqueous—it is in a wet location 410. Pressure sensor P3 isphysically separated from pressure sensor P2 by divider 350. Divider 350is a physical structure that separates the wet location 410 of P2 fromthe dry location 360 of P3. Divider 350 is included when the system ofthe present invention is located on a single substrate. In thisconfiguration, all three pressure sensors (P1, P2, and P3) are locatedon a substrate that includes tube 430, valve 420, divider 350, and theother components of the system.

In one embodiment of the present invention, pressure sensor P3 islocated in close proximity to the eye. Pressure sensor P3 may beimplanted in the eye under the conjunctiva. In such a case, pressuresensor P3 measures a pressure that can be correlated with atmosphericpressure. For example, true atmospheric pressure can be a function ofthe pressure reading of pressure sensor P3. P3 may also be located in adry portion 360 of the subconjunctival space, separate from the drainagelocation. Regardless of location, pressure sensor P3 is intended tomeasure atmospheric pressure in the vicinity of the eye or at the eye'ssurface.

Generally, IOP is a gauge pressure reading—the difference between theabsolute pressure in the eye (as measured by P1) and atmosphericpressure (as measured by P3). Atmospheric pressure, typically about 760mm Hg, often varies in magnitude by 10 mmHg or more. In addition, theeffective atmospheric pressure can vary significantly—in excess of 100mmHg—if a patient goes swimming, hiking, riding in airplane, etc. Such avariation in atmospheric pressure is significant since IOP is typicallyin the range of about 15 mm Hg. Thus, for 24 hour monitoring of IOP, itis desirable to have pressure readings for the anterior chamber (asmeasured by P1) and atmospheric pressure in the vicinity of the eye (asmeasured by P3).

Therefore, in one embodiment of the present invention, pressure readingsare taken by P1 and P3 simultaneously or nearly simultaneously over timeso that the actual IOP can be calculated (as P1−P3 or P1−f(P3)). Thepressure readings of P1 and P3 can be stored in memory 220 by processor215. They can later be read from memory so that actual IOP over time canbe interpreted by a physician.

Pressure sensors P1, P2, and P3 can be any type of pressure sensorsuitable for implantation in the eye. They each may be the same type ofpressure sensor, or they may be different types of pressure sensors. Forexample, pressure sensors P1 and P2 may be the same type of pressuresensor (implanted in the eye), and pressure sensor P3 may be a differenttype of pressure sensor (in the vicinity of the eye).

In another embodiment of the present invention, pressure readings takenby pressure sensors P1 and P2 can be used to control a device thatdrains aqueous from the anterior chamber 340. FIG. 4 is a diagram of onepossible application of the IOP sensor of the present invention thatutilizes the readings of pressures sensors P1 and P2. In FIG. 4,pressure sensor P1 measures the pressure in the anterior chamber 340 ofthe eye. Pressure sensor P2 measures the pressure at a drainage site410.

Numerous devices have been developed to drain aqueous from the anteriorchamber 340 to control glaucoma. Most of these devices are variations ofa tube that shunts aqueous from the anterior chamber 340 to a drainagelocation 410. For example, tubes have been developed that shunt aqueousfrom the anterior chamber 340 to the subconjunctival space thus forminga bleb under the conjunctiva or to the subscleral space thus forming ableb under the sclera. (Note that a bleb is a pocket of fluid that formsunder the conjunctiva or sclera). Other tube designs shunt aqueous fromthe anterior chamber to the suprachoroidal space, the supraciliaryspace, the juxta-uveal space, or to the choroid. In other applications,tubes shunt aqueous from the anterior chamber to Schlemm's canal, acollector channel in Schlemm's canal, or any of a number of differentblood vessels like an episcleral vein. Some tubes even shunt aqueousfrom the anterior chamber to outside the conjunctiva. Finally, in someapplications, no tube is used at all. For example, in a trabeculectomy(or other type of filtering procedure), a small hole is made from thesubconjunctival or subscleral space to the anterior chamber. In thismanner, aqueous drains from the anterior chamber, through the hole, andto a bleb under the conjunctiva or sclera. Each of these differentanatomical locations to which aqueous is shunted is an example of adrainage location 410.

In FIG. 4, a tube 430 with a valve 420 on one end is located with oneend in the anterior chamber 340 and the other end in a drainage location410. In this manner, the tube 430 drains aqueous from the anteriorchamber 340 to the drainage location 410. Valve 420 controls the flow ofaqueous from anterior chamber 340 to drainage location 410. Pressuresensor P1 is located in the anterior chamber or in fluid communicationwith the anterior chamber 340. As shown in the embodiment of FIG. 3,pressure sensor P1 is located upstream from valve 420. In this manner,pressure sensor P1 is located in the subconjunctival space but is influid communication with the anterior chamber 340.

Since pressure sensor P1 measures the pressure in the anterior chamber340 and pressure sensor P2 measures pressure at the drainage location410, the difference between the readings taken by these two pressuresensors (P1-P2) provides an indication of the pressure differentialbetween the anterior chamber 340 and the drainage location 410. In oneembodiment, this pressure differential dictates the rate of aqueous flowfrom the anterior chamber 340 to the drainage location 410.

One complication involved with filtering surgery that shunts theanterior chamber 340 to a drainage location 410 is hypotony—a dangerousdrop in IOP that can result in severe consequences. It is desirable tocontrol the rate of aqueous outflow from the anterior chamber 340 to thedrainage location 410 so as to prevent hypotony. Readings from pressuresensor P1 and pressure sensor P2 can be used to control the flow ratethrough tube 430 by controlling valve 420. For example, valve 420 can becontrolled based on the pressure readings from pressure sensor P1 andpressure sensor P2.

In another embodiment of the present invention, IOP (based on readingsfrom pressure sensor P1 and pressure sensor P3) can be controlled bycontrolling valve 420. In this manner, IOP is the control parameter.Valve 420 can be adjusted to maintain a particular IOP (like an IOP of15 mm Hg). Valve 420 may be opened more at night than during the day tomaintain a particular IOP. In other embodiments, an IOP drop can becontrolled. Immediately after filtering surgery, IOP can dropprecipitously. Valve 420 can be adjusted to permit a gradual drop in IOPbased on readings from pressure sensors P1 and P3.

In another embodiment of the present invention, readings from pressuresensor P2 (or from the difference between pressure sensor P2 andatmospheric pressure as measured by P3) can be used to control valve 420so as to control the morphology of a bleb. One of the problemsassociated with filtering surgery is bleb failure. A bleb can fail dueto poor formation or fibrosis. The pressure in the bleb is one factorthat determines bleb morphology. Too much pressure can cause a bleb tomigrate to an undesirable location or can lead to fibrosis. The pressureof the bleb can be controlled by using the reading from pressure sensorP2 (at drainage location 410—in this case, a bleb). In one embodiment ofthe present invention, the difference between the pressure in the bleb(as measured by P2) and atmospheric pressure (as measured by P3) can beused to control valve 420 to maintain a desired bleb pressure. In thismanner, the IOP pressure sensor of the present invention can also beused to properly maintain a bleb.

Valve 420 can be controlled by microprocessor 215 or a suitable PIDcontroller. A desired pressure differential (that corresponds to adesired flow rate) can be maintained by controlling the operation ofvalve 420. Likewise, a desired IOP, IOP change rate, or bleb pressurecan be controlled by controlling the operation of valve 420.

While valve 420 is depicted as a valve, it can be any of a number ofdifferent flow control structures that meter, restrict, or permit theflow of aqueous from the anterior chamber 340 to the drainage location410. In addition, valve 420 can be located anywhere in or along tube430.

Finally, there are many other similar uses for the present IOP sensor.For example, various pressure readings can be used to determine if tube420 is occluded or obstructed in some undesirable manner. As such,failure of a drainage device can be detected. In a self clearing lumenthat shunts the anterior chamber 340 to a drainage location 410, anundesirable blockage can be cleared based on the pressure readings ofP1, P2, and/or P3.

FIG. 5 is an end cap implementation of an IOP sensor consistent with theprinciples of the present invention. In FIG. 5, pressure sensors P1 andP3 are integrated into an end cap 510. End cap 510 fits in tube 430 soas to form a fluid tight seal. One end of tube 430 resides in theanterior chamber 340, and the other end of tube 430 (where end cap 510is located) is located outside of the anterior chamber 340. Typically,on end of tube 430 resides in the anterior chamber 340, and the otherend resides in the subconjunctival space. In this manner, pressuresensor P1 is in fluid communication with the anterior chamber 340. Sincethere is almost no pressure difference between the anterior chamber 340and the interior of tube 430 that is in fluid contact with the anteriorchamber 340, pressure sensor P1 measures the pressure in the anteriorchamber 340. Pressure sensor P3 is external to the anterior chamber 340and either measures atmospheric pressure or can be correlated toatmospheric pressure.

Typically, tube 430 is placed in the eye to bridge the anterior chamber340 to the subconjunctival space, as in glaucoma filtration surgery. Inthis case, P3 resides in the subconjunctival space. In thisconfiguration, P3 measures a pressure that is either very close toatmospheric pressure or that can be correlated to atmospheric pressurethrough the use of a simple function. Since plug 510 provides a fluidtight seal for tube 430, pressure sensor P3 is isolated from pressuresensor P1. Therefore, an accurate IOP reading can be taken as thedifference between the pressure readings of P1 and P3 (P1−P3). In oneembodiment, a single, thin membrane 520—typically a piezoresistivecrystal—resides in the sensor package and is exposed to P1 on one side(tube side) and P3 on the other side (isolation side), and thus the netpressure on the membrane 520 is recorded by the sensor, providing agauge reading corresponding IOP.

FIGS. 6A and 6B are perspective views of the end cap implementation ofFIG. 5. In this embodiment, pressure sensor P1 is located on one end ofend cap 510 so that it can be located inside tube 430. Pressure sensorP3 is located on the other end of end cap 510 so that it can be locatedoutside of tube 430. A membrane (520) separates P1 from P3. In thismanner, pressure sensor P1 is isolated from pressure sensor P3. Whilepressure sensors P1 and P3 are depicted as being located on oppositesurfaces of a membrane 520 in the end cap 510, they can also be locatedintegral with end cap 510 in any suitable position to facilitate thepressure measurements.

FIGS. 7A and 7B are perspective views of a lumen clearing valveaccording to the principles of the present invention, which can serve ascontrol valve 420. In FIGS. 7A and 7B, the lumen clearing valve 700includes tube 710, housing 720, actuator 730, actuation arm 740, taperedarm 750, pressure sensor P1, and pressure sensor P2. As previouslydescribed with reference to FIGS. 3 and 4, one end of tube 710 islocated in the anterior chamber and the other end of tube 710 is coupledto housing 720. Pressure sensor P1 monitors the pressure in the anteriorchamber. Actuator 730 is located in housing 720. Actuator 730 is coupledto actuation arm 740 which in turn is rigidly connected to tapered arm750. Tapered arm 750 is configured to extend into the lumen of tube 710.Pressure sensor P2 is located at the outflow region of housing 720 (i.e.in the drainage location). The arrows denote the flow of aqueous fromthe anterior chamber to the drainage location.

Housing 720 is generally flat but may have a slight curvature thataccommodates the curvature of the eye. Housing 720 holds actuator 730.Housing 720 also holds the actuation arm 740 and tapered arm 750. Tube710 is fluidly coupled to a channel located in the interior of housing720. This channel conducts aqueous from the anterior chamber (throughtube 710) and to the drainage location. Housing 720 can be made of anyof a number of different biocompatible materials such as stainlesssteel.

Actuator 730 moves actuation arm 740 back and forth in a plane. In thismanner, actuation arm 740 oscillates or reciprocates when a force isapplied on it by actuator 730. Since tapered arm 750 is rigidly coupledto actuation arm 740, it also oscillates or reciprocates in tube 710.Actuator 730 can be based any of a number of different known methodssuch as electromagnetic actuation, electrostatic actuation,piezoelectric actuation, or actuation by shape memory alloy materials.Actuation arm 740 can be moved by actuator 730 at a low repetition rate(for example, a few Hertz) or a high actuation rate (for example,ultrasonic).

Tapered arm 750 is sized to fit in tube 710. In this manner, tapered arm750 can be made to oscillate back and forth in tube 710 to clear anymaterial that is blocking tube 710. Tapered arm 750 has a generallypointed end that is located in tube 710. As shown, tapered arm 750 alsohas a larger tapered portion that can serve to restrict flow throughtube 710 thus functioning as a valve. In this manner, not only cantapered arm 750 be oscillated to clear material blocking tube 710, butit can also be moved to a position that partially obstructs flow throughtube 710. The tapered designed of arm 750 allows for a variable level offlow restriction through tube 710 by the varying the position of arm 750relative to housing 720 and tube 710.

When used as a valve, tapered arm 750 can restrict the amount of aqueousthat enters the drainage location and exits the anterior chamber.Controlling aqueous flow can reduce the chances of hypotony afterfiltration surgery, maintain a suitable IOP, and control the amount ofstagnant aqueous in the drainage location. When the drainage location isa subconjunctival bleb, controlling the amount of stagnant aqueous inthe bleb can help maintain proper bleb morphology and reduce the amountof fibrosis. Too much stagnant aqueous in a bleb can lead to fibrosis.It has been postulated that fibroblasts form in stagnant aqueous andthat too much tension on the bleb wall (i.e. too high a pressure in thebleb) can lead to bleb failure. The use of tapered arm 750 as a valve,therefore, can lead to proper bleb maintenance which decreases thechances of these deleterious side effects.

The lumen clearing valve system 700 can be controlled based on readingsfrom P1, P2, and P3 as described above. The lumen clearing valve system700 of the present invention can be made using a MEMS process in whichlayers are deposited on a substrate that forms part of housing 720. Allof the elements of the lumen clearing valve system 700 can be locatedon, under, or embedded in a plate that extends into the drainagelocation—much like currently available glaucoma drainage devices.

FIG. 8 is a perspective view of a lumen clearing valve with a fiberclearing member according to the principles of the present invention.The embodiment of FIG. 8 is similar to that of FIG. 7, except that FIG.8 also depicts a needle head 810 that is located in the drainagelocation. Typically, the drainage location is in the subconjunctivalspace. In this manner, a bleb in the subconjunctival space receives theaqueous that exits the housing 710. Needle head 810 can be oscillated tokeep the bleb clear of fibers or to reduce fibrosis (which is one causeof bleb failure). In this manner, when actuation arm 740 is moved,needle head 810 is moved in the drainage location (in this case, ableb). Needle head 810 can dislodge fibers and prevent the build up offibrotic tissue.

FIG. 9 is a perspective view of a lumen clearing valve with an aqueousdispersion member to clear fibrosis according to the principles of thepresent invention. The embodiment of FIG. 9 is similar to that of FIG.7, except that FIG. 9 also depicts a needle head 910 that is located inthe drainage location. In this embodiment, needle head 910 may serve toclear fibers in the drainage location and/or disperse aqueous to thedrainage location. The outlet end of housing 920 is open to allowaqueous to flow to the drainage location. Needle head 910 is locatednear the outlet within the housing. Needle head 910 is generally broadand blunt so that when it oscillates, aqueous is distributed to thedrainage location. Fluid passes from tube 710 to the drainage locationvia microchannels 930, which are typically etched into needle head 910.The dispersion of aqueous can help reduce the formation of resistance atthe drainage location, typically created by bleb formation and/orfibrotic growth, by providing a larger effective area in the drainagelocation, decreasing bleb height, and/or reducing bleb pressure in orderto more properly manage bleb morphology. Additionally, the dispersion ofaqueous can aid the flow of drainage by providing a mechanical means ofovercoming the flow resistance associated with the drainage location,typically created by bleb formation and/or fibrotic growth.

FIG. 10 is a perspective view of a lumen clearing valve with hybridexternal member according to the principles of the present invention.The embodiment of FIG. 10 is similar to the embodiment of FIG. 9. InFIG. 10, a broad needle head 1010 and additional drainage holes 1030allow for a wide dispersion of aqueous in the drainage location(typically, a subconjunctival bleb). Fluid passes from tube 710 to thedrainage location via microchannels 930, which are typically etched intoneedle head 1010. In FIG. 10, housing 1020 has a broad outlet end thatincludes multiple drainage holes 1030. In addition, the broad end ofhousing 1020 is open to allow aqueous to flow through this wide opening.Therefore, in the embodiment of FIG. 10, aqueous flows from the anteriorchamber through tube 710, through housing 1020 and out of drainage holes1030 and the broad end of housing 1020 into the drainage location. Whenneedle head 1010 is oscillated, it can serve to clear fibers from thedrainage location. It can also disperse aqueous to the drainagelocation.

The embodiments of FIGS. 7-10 can be operated in two differentmodes—lumen clearing mode in which the tapered arm 750 oscillates ormoves and valve mode in which the tapered arm 750 is maintained in aparticular position to restrict fluid flow through tube 710. In lumenclearing mode, tapered arm 750 is moved or oscillated to clear fibrousmaterial from the interior of tube 710 and/or the drainage location. Inlumen clearing mode, tapered arm 750 can also help to disperse aqueousin the drainage location.

When operating as a valve, tapered arm 750 can be maintained in aparticular position to restrict the flow of aqueous through tube 710.The position of tapered arm 750 can be changed over time based onpressure readings from pressure sensors P1, P2, and/or P3 as describedabove with respect to FIGS. 3-6. In this manner, any of the followingcan be the basis for control of the tapered arm 750: IOP, pressure inthe bleb, fluid flow rate, etc.

FIG. 11A is a diagram of a two lumen valve and pressure sensor systemaccording to the principles of the present invention. In FIG. 11A, tube710 of the active valve/lumen clearing system bridges the anteriorchamber and a drainage location. A second tube 430 includes end cap 510as described in FIG. 5. The system of FIG. 11A combines the pressuresensor of FIGS. 5 and 6 with the active valve/lumen clearing device ofFIGS. 7-10, wherein the latter can serve as control valve 420. In thismanner, one tube (430) can be used to measure IOP, while a second tube(710) can be used for draining aqueous. Fluidic communication between adry location 360 and the P3 sensing portion of end cap 510 can beprovided by tube 1100. FIG. 11B is another possible arrangement, whereina single tube resides in the anterior chamber 340. In FIG. 11B, end cap510 is located in an opening in tube 430.

FIGS. 12A and 12B are cross section views of dual tubing that can beused with the system of the present invention. In FIG. 12A, two lumens,430 and 710, are contained in a single tube. FIG. 12A shows this dualbore tubing arrangement. In FIG. 12B, two lumens, 430 and 710, arecontained in two separate tubes that are joined together. FIG. 12B showsthis dual-line tubing arrangement. Other variations of a dual lumendevice can also be used in conjunction with the present invention.

FIG. 13 is a perspective view of a two lumen valve and pressure sensorsystem according to the principles of the present invention. In FIG. 13,two tubes, 430 and 710, are connected at one end (the end that residesin the anterior chamber) and are separated at the other end (in thiscase, the end that resides in the subconjunctival space). Tube 430 hasend cap 510 that measures IOP. Tube 710 receives tapered arm 750.Tapered arm 750 can serve to clear the interior of tube 710. Tube 750can also act as a valve that can partially or totally occlude theinterior of tube 710. Tapered arm 750 is coupled to the any of thesystems depicted in FIGS. 7-10. A barrier 350 separates P3 from theoutlet of 710, typically the drainage location 410. In this manner, P3is in a “dry” space 360 and measures an approximation of atmosphericpressure. The outlet end of 710 (shown adjacent to tapered arm 750) islocated in a “wet” space or drainage location such as 410. As notedabove, P2 is located in this “wet” space.

Power for the pressure monitoring system or active drainage system maybe supplied by a power source 205 as described above. As shown in FIG.2, power source 205 is coupled to power generator 1410. One example ofpower generator 1410 is shown in FIG. 14. In FIG. 14, power generator1410 has a micro-generator 1420 coupled to a rotor 1430. In thisexample, as rotor 1430 turns, micro-generator 1420 produces power. Assuch, the operation of power generator 1410 is much like that of anyconventional generator. While rotor 1430 is shown as having four paddlesconnected to a shaft, any rotor design may be employed. Moreover, anyother type of apparatus that converts a fluid flow into power may beemployed. FIG. 14 is intended only as one example.

Power generator 1410 is capable of harnessing the aqueous fluid flowfrom the anterior chamber 340 to the drainage location 410. Since thegeneral purpose of any glaucoma drainage device is to shunt aqueous fromthe anterior chamber 340 to a drainage location 410, aqueous flows fromthe anterior chamber 340 to the drainage location 410 (in this case,through a tube, such as tube 430). There is a natural pressuredifference between the fluid pressure in the anterior chamber 340 andthe fluid pressure in the drainage location 410. This pressuredifference causes aqueous to flow from the anterior chamber 340 to thedrainage location 410. Power generator 1410 converts this aqueous fluidflow into power.

In a typical example, the aqueous flowing through the tube 430 turnsrotor 1430 at about 1 revolution per minute based on an aqueous flowrate of about two microliters per minute. If the pressure differencebetween the anterior chamber 340 and the drainage location 410 is abouteight millimeters of mercury, the transferable potential power is about25 nanowatts (or about two milliJoules of energy) per day. This powercan be stored in power source 205 and used to power the systems(pressure sensors, telemetry, active valve, etc.) described in thisapplication.

FIG. 15 is an end view of one embodiment of a rotor according to theprinciples of the present invention. In FIG. 15, rotor 1430 has a shaftconnected to four paddles. Rotor 1430 is located in tube 430 to harnessthe fluid flowing through the tube. The arrows denote the direction ofaqueous fluid flow through tube 430 and the corresponding direction ofrotation of rotor 1430. As noted, FIG. 15 depicts one of many possibleconfigurations for rotor 1430.

FIG. 16 is a diagram of one possible location of a power generator in aglaucoma drainage system according to the principles of the presentinvention. In the example of FIG. 16, power generator 1410 is located inor along tube 430. Tube 430 shunts the anterior chamber 340 to thedrainage location 410. Valve 420 is located at the end of tube 430 aspreviously described. In this example, the power generated by powergenerator 1410 is used to power valve 420 (and other components of thesystem).

FIG. 17 is a diagram of another possible location of a power generatorin a glaucoma drainage system according to the principles of the presentinvention. In the example of FIG. 17, power generator 1410 is located atthe end of tube 430. Here, power generator 1410 performs two functions:it generates power and it acts as a valve. Since power generator 1410resists the flow of fluid through tube 430, this flow resistance can beused to control the rate of aqueous flowing through tube 430. In otherwords, power generator 1410 can be operated as an active valve.Moreover, the rotation of the rotor can function to clear the lumen (asdescribed above).

In the example of FIG. 17, the micro-generator 1420 can be controlled tovary the flow resistance of rotor 1430. When micro-generator 1420 is asimple magnetic core and coil generator (like the typical electricgenerator), the distance between the magnetic core and the coil can bevaried to vary the force required to turn rotor 1430. The more forcerequired to turn rotor 1430, the more resistance to aqueous flowingthrough tube 430. Conversely, the less force required to turn rotor1430, the less resistance to aqueous flowing through tube 430. Thisresistance to aqueous flow can be controlled to maintain a desired IOP.

Regardless of whether the glaucoma drainage device has a power generatoror operates on stored energy, a power savings method of operating thedevice may be beneficial. FIG. 18 is a flow chart of one method ofoperating the glaucoma drainage device of the present invention so as toconserve power. In 1810, the system is powered on. In 1820, IOP ismeasured. IOP may be measured as described above. If IOP is in range,then in 1830, the device powers off (i.e. is in sleep mode) for a timeX. If IOP is out of range, then in 1840, the valve is adjustedaccordingly. In 1850, IOP is measured. If IOP is in range, then in 1830,the device powers off (i.e. is in sleep mode) for a time X. If IOP isout of range, then in 1840, the valve is adjusted accordingly. Thisiterative process can be repeated as necessary to maintain IOP in adesired range.

Accordingly, with the operation depicted in FIG. 18, the glaucomadrainage device of the present invention takes periodic IOP measurementsand makes adjustments accordingly. The time interval X between IOPmeasurements can be any time period. For example, IOP measurements canbe made every ten minutes or every hour. A range of values can be setthat determine whether the IOP readings are in range or out of range.For example, an IOP above 15 mm Hg may be considered too high. If an IOPmeasurement is taken that is above 15 mm Hg, it is out of range, and thevalve is adjusted accordingly. The IOP measurement in 1850 may also berepeated at any time interval to adjust the valve. For example, the IOPreading in 1850 may be repeated every minute in the process of adjustingthe valve.

From the above, it may be appreciated that the present inventionprovides a lumen clearing valve that can be controlled by an IOP sensor.The present invention provides a valve-like device that can clear alumen, disperse aqueous, and/or clear fibrous material from a drainagelocation. The present invention also provides an implantable powergenerator that can be used to power such a system. The present inventionis illustrated herein by example, and various modifications may be madeby a person of ordinary skill in the art.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. A glaucoma drainage device comprising: an active valve configured tobe located between an anterior chamber of an eye and a drainagelocation; a power source coupled to the active valve; and a controllercoupled to the power source; wherein the controller directs power fromthe power source to the active valve based on a pressure.
 2. Theglaucoma drainage device of claim 1 wherein the pressure is intraocularpressure and the controller directs power from the power source to theactive valve when the intraocular pressure is not in a range.
 3. Theglaucoma drainage device of claim 1 wherein the drainage location isselected from the group consisting of: a subconjunctival space of theeye, a suprachoroidal space of the eye, a supraciliary space of the eye,a subscleral space of the eye, and outside the eye.
 4. The glaucomadrainage device of claim 1 wherein the active valve comprises: a housingwith an open outlet end; a tube in fluid communication with the housing;an actuator located in the housing; an actuation arm located at leastpartially in the housing, the actuation arm coupled to the actuator; anda tapered arm rigidly coupled to the actuation arm, a tapered end of thetapered arm located at least partially in the tube.
 5. The glaucomadrainage device of claim 4 wherein the controller controls the positionof the tapered arm so that it partially obstructs the tube therebyrestricting fluid flow through the tube.
 6. The glaucoma drainage deviceof claim 4 further comprising: a needle head connecting the actuationarm to the tapered arm, the needle head located opposite the tapered endof the tapered arm.
 7. The glaucoma drainage device of claim 6 whereinthe controller controls the actuator to move the needle head in adrainage location to disperse aqueous in the drainage location.
 8. Theglaucoma drainage device of claim 1 further comprising: a first pressuresensor located in fluid communication with an anterior chamber of aneye; and a second pressure sensor located in the drainage location;wherein a difference between readings from the first pressure sensor andthe second pressure sensor approximates a pressure differential betweenthe anterior chamber and the drainage location; and further wherein thecontroller uses the pressure differential to control the active valve.9. The glaucoma drainage device of claim 5 further comprising; a firstpressure sensor located in fluid communication with an anterior chamberof an eye; and a remote pressure sensor located remotely from the firstpressure sensor such that the remote pressure sensor measures orapproximates atmospheric pressure. wherein a difference between readingsfrom the first pressure sensor and the remote pressure sensorapproximates intraocular pressure; and further wherein the controlleruses intraocular pressure to control the active valve.
 10. Anintraocular pressure sensor system comprising: a first pressure sensorlocated in fluid communication with an anterior chamber of an eye; aremote pressure sensor located remotely from the first pressure sensorsuch that the remote pressure sensor measures or approximatesatmospheric pressure; a controller configured to read the first andsecond pressure sensors; and a power source coupled to the controller;wherein a difference between readings from the first pressure sensor andthe remote pressure sensor approximates intraocular pressure; andfurther wherein the controller reads the first pressure sensor and thesecond pressure sensor once during a time period.
 11. The pressuresensor system of claim 10 further comprising: a barrier that separatesthe first pressure sensor from the remote pressure sensor.
 12. Anintraocular pressure sensor system comprising: a first pressure sensorlocated in fluid communication with an anterior chamber of an eye; asecond pressure sensor located in a drainage location; a controllerconfigured to read the first and second pressure sensors; and a powersource coupled to the controller; wherein a difference between readingsfrom the first pressure sensor and the second pressure sensorapproximates a pressure differential between the anterior chamber andthe drainage location; and further wherein the controller reads thefirst pressure sensor and the second pressure sensor once during a timeperiod.
 13. An intraocular pressure sensor system comprising: a firstpressure sensor located in a drainage location; a remote pressure sensorlocated remotely from the first pressure sensor such that the remotepressure sensor measures or approximates atmospheric pressure; acontroller configured to read the first and second pressure sensors; anda power source coupled to the controller; wherein a difference betweenreadings from the first pressure sensor and the remote pressure sensorapproximates pressure in the drainage location; and further wherein thecontroller reads the first pressure sensor and the second pressuresensor once during a time period.
 14. A glaucoma drainage devicecomprising: an active valve configured to be located between an anteriorchamber of an eye and a drainage location; a power source coupled to theactive valve; a controller coupled to the power source; a first pressuresensor located in fluid communication with the anterior chamber; asecond pressure sensor located in the drainage location; and a thirdpressure sensor located remotely from the first and second pressuresensors; wherein the controller reads the first, second, and thirdpressure sensors once during a period of time.
 15. The glaucoma drainagedevice of claim 14 wherein the period of time is greater than thirtyseconds and less than one hour.
 16. The glaucoma drainage device ofclaim 14 wherein the controller computes an intraocular pressure basedon a pressure read from the first second, or third pressure sensor. 17.The glaucoma drainage device of claim 14 wherein the controller directspower from the power source to the active valve based on a pressure readfrom the first second, or third pressure sensor.
 18. The glaucomadrainage device of claim 17 wherein the controller subsequently readsthe first, second, and third pressure sensors and directs furtheradjustment of the active valve.
 19. The glaucoma drainage device ofclaim 14 wherein the controller adjusts the active valve based on apressure read from the first second, or third pressure sensor to changethe intraocular pressure of an eye.